Soil microbial biomass, functional microbial diversity, and nematode community structure as affected by cover crops and compost in an organic vegetable production system
Highlights
► Cover crops and compost affect soil microbial biomass and functional diversity. ► Rye-vetch mixture significantly increased soil respiration and microbial biomass. ► Nematode population differences leveled off by the end of the final growing season. ► Compost application increased microbial biomass and functional microbial diversity. ► Compost influenced treatment separation in principal component analysis.
Introduction
A high and increasing demand for sustainably produced fruits and vegetables have encouraged growers to transition to sustainable and organic production systems (Klonsky, 2004). Such ecologically sound systems have the potential to address a number of ongoing issues in mainstream agriculture namely pollution due to chemical fertilizers and pesticides, production loses due to pest and disease pressure, soil degradation, loss of soil fertility and productivity. One of the core philosophies of organic production systems is the development of healthy and productive soil that provide essential nutrients for plant growth, supports diverse and active soil biotic communities, and balances the entire farm ecosystem (Insam, 2001, Mäder et al., 2002). Soil biology is directly linked to agricultural sustainability as it is the driving force behind decomposition processes that break down complex organic molecules and substances and convert them to plant available forms (Friedel et al., 2001). Large, stable, and active soil microbial community is an underpinning for sustaining the productivity of soils under sustainable and organic farming systems. To develop such systems growers adopt strategies such as crop rotations, cover cropping, and application of organic amendments (manures and composts) that significantly increase soil organic matter (SOM) and improve soil biology and quality (Bending et al., 2002, Buyer et al., 2010)
Cereal rye (Secale cereale L.) and hairy vetch (Vicia villosa Roth.) (from now on referred to as rye and vetch, respectively) are among the most common cover crops used in regions with temperate climate because of their winter hardiness, the ability to produce considerable biomass, and, in case of vetch, capacity to fix atmospheric nitrogen (Abdul-Baki et al., 1996). When mowed and incorporated these cover crops add SOM, improve soil structure and increase soil biological activity (Carrera et al., 2007, Lundquist et al., 1999). In a three-year study, Buyer et al. (2010) demonstrated that the integration of both rye and vetch cover crop into crop rotations increased soil microbial biomass (SMB) considerably. Along with cover crops, use of compost and manure is considered as an integral component for organic production as it provides essential plant nutrients, adds SOM, and improves soil quality and structure (Russo and Webber, 2007). Application of manure and compost on agricultural lands has been shown to positively increase and enrich soil food web (bacteria, fungi, protozoan and nematode density) and also affect a number of soil characteristics, including SOM, and soil respiration (Carrera et al., 2007, Ferris et al., 2004, Lundquist et al., 1999, Treonis et al., 2010). With increasing number of growers using cover crops and organic amendments in their production systems, it becomes all the more important to better understand the effects of such strategies on soil microorganisms as they are directly involved in organic matter decomposition and nutrient cycling. After soil incorporation, nutrients available in cover crops and organic amendments have to pass through a decomposition pathway which involves a number of soil microorganisms including, bacteria, fungi, and nematodes. Thus, the quality and quantity of plant residues entering the soil can significantly influence soil microorganisms and soil microbial processes (Govaerts et al., 2007). Both crop residue and SOM quality have the potential to increase functional diversity in soil microbial communities (Bending et al., 2002).
Soil contains enormous number of diverse living organisms that influence various ecosystem processes, including formation of organic matter, recycling of nutrients, modification of soil physical and chemical properties, and suppression of pests and diseases (Coleman et al., 1978). Biological characteristics of soil play a vital role in defining soil quality and health. Soil quality is an effective indicator of soil fertility and reflects changes in soil properties which are both inherent and anthropogenic. Soil quality can be estimated and quantified through evaluation of physical, biochemical, or microbial parameters (Glover et al., 2000). A number of soil microbial parameters such as SMB, respiration, metabolic quotient (qCO2), and community profiles have the potential for use as diagnostic indicators of soil quality. Such indicators have been widely used in discerning changes in soil quality and to make comparisons between different soil types and contrasting management systems (Bending et al., 2004, Schloter et al., 2003).
In this study we compared four organic tomato production systems, which differ, based on plant residues and compost inputs. The specific aim of this study was to investigate the impact of cover crop and compost on soil chemical and biological characteristics and tomato yield. Under different cover crop and compost treatments we evaluated parameters such as SMB, nematode community composition, and microbial diversity of aerobic microbial community that rapidly respond to management systems in a short period of time. A simple approach to measure soil microbial functional diversity is to examine the number of different C substrates that are metabolized by the culturable microbial community. This approach of substrate utilization pattern can be obtained using the Biolog-EcoPlate™ system (Garland and Mills, 1991, Zak et al., 1994). The Biolog-EcoPlate™ system assesses the ability of microbial populations toutilize substrates over time and the speed at which the substrates are utilized. The technique generates a community level physiological profile (CLPP) of aerobicmicrobial communities (Garland and Mills, 1991). In our study we hypothesized that: (1) a cover crop mixture of rye-vetch would enhance microbial biomass, and affect nematode counts and microbial functional diversity when compared to a rye only cover crop and (2) application of compost would positively influence the abundance of SMB, improve soil microbial functional diversity, and increase tomato yield.
Section snippets
Field preparation and production techniques
This study was conducted from 2005 to 2009 at the Horticulture Teaching and Research Center (HTRC), Michigan State University, Holt, MI. The soil was a Capac loam with 0–3% slope. Capac loam is a somewhat poorly drained, moderately to moderately slowly permeable soil formed in loamy glacial till on the low parts of moraines and till plains. The soil at the research site was under transition (starting 2005) from a non-organic corn/soybean rotation to an organic tomato production system. Although
Cover crop biomass and tomato yield
Amount of biomass produced by cover crops varied each year. Over all biomass produced in 2007 was lower than 2008 and 2009 (Fig. 1). Differences in biomass between cover crop treatments were largely due to crop type and compost treatments. Rye-vetch-no-compost treatment consistently performed below average in all the years. This is partly due to low seeding rate of rye in rye-vetch treatment, low fertility, and poor establishment of vetch as a result of late planting dates. Rye-compost
Discussion
The objective of this study was to understand changes in below ground biology brought out by two very commonly used organic amendments, cover crops and compost, under an organic production system. We focused on rye and arye-vetch mixture, as they are suitable to temperate climatic regions and a widely accepted cover crop system. During the course of our study the amount of cover crop biomass added to the treatments varied between treatments. Although organic growers generally mix rye with a
Conclusion
Overall our results demonstrate that soil management practices, such as the practice of cover cropping and compost application can enhance soil biological activity. Soil biological properties such as respiration, microbial biomass, nematode population, and microbial functional diversity can be used an indicator of management induced, changes to soil quality. For most soil biological properties evaluated, use of rye or rye-vetch mixture did not lead to major differences; however, the use of
Acknowledgments
We thank Aristarque Djoko, Buck Counts, Pamela Nichol, and the support staff at Horticulture Teaching and Research Center at Michigan State University for their assistance with composting, crop planting, irrigation, and harvesting operations. This work was supported by a grant from the United States Department of Agriculture (USDA Grant no. 2005-51300-02391.
References (55)
- et al.
Interaction between crop residue and soil organic matter quality and the functional diversity of soil microbial communities
Soil Biol. Biochem.
(2002) - et al.
Microbial and biochemical soil quality indicators and their potential for differentiating areas under contrasting agricultural management regimes
Soil Biol. Biochem.
(2004) - et al.
Factors affecting soil microbial community structure in tomato cropping system
Soil Biol. Biochem.
(2010) - et al.
Evaluating soil management with microbial community-level physiological profiles
Appl. Soil Ecol.
(2005) - et al.
Organic and synthetic fertility amendments influence soil microbial, physical and chemical properties on organic and conventional farms
Appl. Soil Ecol.
(2002) - et al.
Effects of cover crops, compost, and manure amendments on soil microbial community structure in tomato production systems
Appl. Soil Ecol.
(2007) - et al.
Soil management to enhance bacterivore and fungivore nematode populations and their nitrogen mineralization function
Appl. Soil Ecol.
(2004) - et al.
Dynamics of nematode communities in tomatoes grown in conventional and organic farming systems, and their impact on soil fertility
Appl. Soil Ecol.
(1996) - et al.
Soil organic matter and biological soil quality indicators after 21 years of organic and conventional farming
Agric. Ecosyst. Environ.
(2007) Analysis and interpretation of community-level physiological profiles in microbial ecology
FEMS Microbiol. Ecol.
(1997)
Soil bacterial functional diversity as influenced by organic amendment application
Bioresour. Technol.
Systematic method for rating soil quality of conventional, organic, and integrated apple orchards in Washington state
Agric. Ecosyst. Environ.
Influence of tillage, residue management, and crop rotation on soil microbial biomass and catabolic diversity
Appl. Soil Ecol.
Dynamics of soil microbial biomass and activity in conventional and organic farming systems
Soil Biol. Biochem.
Developments in soil microbiology since the mid-1960s
Geoderma
The effects of biocidal treatments on metabolism in soil-I. Fumigation with chloroform
Soil Biol. Biochem.
Changes in microbial biomass and community composition, and soil carbon and nitrogen pools after incorporation of rye into three California agricultural soils
Soil Biol. Biochem.
Mechanisms of nematode suppression by organic soil amendments—a review
Appl. Soil Ecol.
Response of soil microbial communities to compost amendments
Soil Biol. Biochem.
Indicators for evaluating soil quality
Agric. Ecosyst. Environ.
Soil microbial biomass and activity in organic tomato farming systems: effects of organic inputs and straw mulching
Soil Biol. Biochem.
A critique of microbial metabolic quotient (qCO2) as a bioindicator of disturbance and ecosystem development
Soil Biol. Biochem.
Functional diversity of microbial communities – a quantitative approach
Soil Biol. Biochem.
Fresh market tomato production in a low-input alternative system using cover-crop mulch
HortScience
Trophic interactions in soils as they affect energy and nutrient dynamics. IV. Flows of metabolic and biomass carbon
Microb. Ecol.
Soil organic matter
Soil enzyme activities and biodiversity measurements as integrative microbiological indicators
Cited by (0)
- 1
Tel.: +1 517 355 5191x1410; fax: +1 517 353 0890.